[PATCH] scsi: use sector_div instead of do_div

[PATCH] scsi: use sector_div instead of do_div

[Arnd Bergmann]

do_div is the wrong way to divide a sector_t, as it is less
efficient when sector_t is 32-bit wide. With the upcoming
do_div optimizations, the kernel starts warning about this:

drivers/scsi/scsi_debug.c: In function 'dif_store':
include/asm-generic/div64.h:207:28: warning: comparison of distinct pointer types lacks a cast

This changes the code to use sector_div instead, which always
produces optimal code.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
Found on the ARM randconfig build today, after I merged Nico's patches
for linux-next

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index dfcc45bb03b1..ec622ba9864a 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -678,7 +678,7 @@ static void *fake_store(unsigned long long lba)
 
 static struct sd_dif_tuple *dif_store(sector_t sector)
 {
-	sector = do_div(sector, sdebug_store_sectors);
+	sector = sector_div(sector, sdebug_store_sectors);
 
 	return dif_storep + sector;
 }
@@ -2780,7 +2780,7 @@ static unsigned long lba_to_map_index(sector_t lba)
 		lba += scsi_debug_unmap_granularity -
 			scsi_debug_unmap_alignment;
 	}
-	do_div(lba, scsi_debug_unmap_granularity);
+	sector_div(lba, scsi_debug_unmap_granularity);
 
 	return lba;
 }

[PATCH] scsi: use sector_div instead of do_div

[Johannes Thumshirn]

On Fri, 2015-11-20 at 17:38 +0100, Arnd Bergmann wrote:
> do_div is the wrong way to divide a sector_t, as it is less
> efficient when sector_t is 32-bit wide. With the upcoming
> do_div optimizations, the kernel starts warning about this:
> 
> drivers/scsi/scsi_debug.c: In function 'dif_store':
> include/asm-generic/div64.h:207:28: warning: comparison of distinct
> pointer types lacks a cast
> 
> This changes the code to use sector_div instead, which always
> produces optimal code.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> Found on the ARM randconfig build today, after I merged Nico's
> patches
> for linux-next
> 
> diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
> index dfcc45bb03b1..ec622ba9864a 100644
> --- a/drivers/scsi/scsi_debug.c
> +++ b/drivers/scsi/scsi_debug.c
> @@ -678,7 +678,7 @@ static void *fake_store(unsigned long long lba)
> ?
> ?static struct sd_dif_tuple *dif_store(sector_t sector)
> ?{
> -	sector = do_div(sector, sdebug_store_sectors);
> +	sector = sector_div(sector, sdebug_store_sectors);
> ?
> ?	return dif_storep + sector;
> ?}
> @@ -2780,7 +2780,7 @@ static unsigned long lba_to_map_index(sector_t
> lba)
> ?		lba += scsi_debug_unmap_granularity -
> ?			scsi_debug_unmap_alignment;
> ?	}
> -	do_div(lba, scsi_debug_unmap_granularity);
> +	sector_div(lba, scsi_debug_unmap_granularity);
> ?
> ?	return lba;
> ?}
> 
> --
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Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>

[PATCH] scsi: use sector_div instead of do_div

[Sagi Grimberg]

On 20/11/2015 18:38, Arnd Bergmann wrote:
> do_div is the wrong way to divide a sector_t, as it is less
> efficient when sector_t is 32-bit wide. With the upcoming
> do_div optimizations, the kernel starts warning about this:
>
> drivers/scsi/scsi_debug.c: In function 'dif_store':
> include/asm-generic/div64.h:207:28: warning: comparison of distinct pointer types lacks a cast
>
> This changes the code to use sector_div instead, which always
> produces optimal code.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Reviewed-by: Sagi Grimberg <sagig@mellanox.com>

[PATCH] scsi: use sector_div instead of do_div

[Hannes Reinecke]

On 11/20/2015 05:38 PM, Arnd Bergmann wrote:
> do_div is the wrong way to divide a sector_t, as it is less
> efficient when sector_t is 32-bit wide. With the upcoming
> do_div optimizations, the kernel starts warning about this:
> 
> drivers/scsi/scsi_debug.c: In function 'dif_store':
> include/asm-generic/div64.h:207:28: warning: comparison of distinct pointer types lacks a cast
> 
> This changes the code to use sector_div instead, which always
> produces optimal code.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> Found on the ARM randconfig build today, after I merged Nico's patches
> for linux-next
> 
> diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
> index dfcc45bb03b1..ec622ba9864a 100644
> --- a/drivers/scsi/scsi_debug.c
> +++ b/drivers/scsi/scsi_debug.c
> @@ -678,7 +678,7 @@ static void *fake_store(unsigned long long lba)
>  
>  static struct sd_dif_tuple *dif_store(sector_t sector)
>  {
> -	sector = do_div(sector, sdebug_store_sectors);
> +	sector = sector_div(sector, sdebug_store_sectors);
>  
>  	return dif_storep + sector;
>  }
> @@ -2780,7 +2780,7 @@ static unsigned long lba_to_map_index(sector_t lba)
>  		lba += scsi_debug_unmap_granularity -
>  			scsi_debug_unmap_alignment;
>  	}
> -	do_div(lba, scsi_debug_unmap_granularity);
> +	sector_div(lba, scsi_debug_unmap_granularity);
>  
>  	return lba;
>  }
> 
Reviewed-by: Hannes Reinecke <hare@suse.com>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		               zSeries & Storage
hare at suse.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 N?rnberg
GF: F. Imend?rffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG N?rnberg)

[PATCH] scsi: use sector_div instead of do_div

[Martin K. Petersen]

>>>>> "Arnd" == Arnd Bergmann <arnd@arndb.de> writes:

Arnd> do_div is the wrong way to divide a sector_t, as it is less
Arnd> efficient when sector_t is 32-bit wide. With the upcoming do_div
Arnd> optimizations, the kernel starts warning about this:

Applied.

-- 
Martin K. Petersen	Oracle Linux Engineering